1. Field of the Invention
The present invention relates to a novel therapeutic use of basic aminoacids, acylated basic aminoacids and their pharmacologically acceptable salts for the prophylaxis of diseases or the therapeutic treatment of cellular disorders accompanied by high levels of ceramide. In particular, the present invention relates to the use of L-carnitine, acyl L-carnitine derivatives and pharmacologically acceptable salts thereof for the prophylaxis of diseases or the therapeutic treatment of cellular disorders accompanied by high levels of ceramide.
2. Description of the Background
Ceramide is the basic molecule for the sphingolipids structure and metabolism thereof. All sphingolipids contain ceramide as main hydrophilic component and originate from ceramide through biosynthesis pathways which mainly modify the 1-hydroxy position thereof. In turn, sphingolipids play an important role in the transduction of the signal across the cellular membrane.
Ceramide plays an important role in the transduction of the signal across the cellular membrane. Molecules able to act upon the intracellular receptors (i.e. calcitriol) or the transmembrane receptors [i.e., gamma interferon (IFN-.gamma.), interleukin-1 (IL-1) and the nerve growth factor (NGF)] hydrolize sphingomyelin to ceramide. Ceramide activates phosphatases and protein kinases and, from a biological point of view, induces cellular apoptosis, growth and cell differentiation, modulates the expression of cydooxygenases and phospholipases and the activation of kB nuclear factors (NFkB) [Kuno, K. et al., J. Leukoc. Biol., 56(5): 542-7; Cifone, M. G. et al., J. Exp. Med., 180(4): 1547-52; Kolesnick R., Mol. Chem. Neuropathol., 21(2-3): 287-97; Jarvis, W. D. et al., Proc. Natl. Acad. Sci. U.S.A., 91(1): 73-7; Obeid, L. M. et al., Science, 259(5102): 1769-71].
It has now been found that variations in the concentration or in the metabolism of ceramide contribute to the pathogenesis of numerous illnesses or contribute to induce metabolic cellular disorders. Unfortunately, to date, there exist no methods to reduce ceramide levels in vivo.
Accordingly, one object of this invention is to provide a novel use of basic aminoacids, acylated basic aminoacids and their pharmacologically acceptable salt for reducing ceramide levels in vivo.
A second object of the present invention is to provide a novel use of basic aminoacids, acylated basic aminoacids and their pharmacologically acceptable salt for the prophylaxis of diseases or the therapeutic treatment of cellular disorders accompanied by high levels of ceramide.
It has in fact been found that administration of high doses of basic aminoacids, low molecular weight basic compounds or acyl derivatives thereof and pharmacologically acceptable salts thereof reduces ceramide levels and such compounds can thus be used for the treatment of diseases characterized by high levels of ceramide.
In particular, it has been found that basic aminoacids such as arginine, lysine, histidine, ornithine, and carnitine or acyl derivatives thereof and pharmacologically acceptable salts thereof can be used for the treatment of diseases characterized by high levels of ceramide.
In accordance with the invention, a novel use of basic aminoacids, basic aminoacid acyl derivatives and pharmacologically acceptable salts thereof is provided for lowering the levels of ceramide in vivo.
Suitable aminoacids include any amirnoacid with a basic charge such as argnine, lysine, histidine, ornithine and carnitine. These compounds are commercially available. Preferably, L-aminoacids are used. More preferably, carnitine is used. These compounds can be used as free aminoacids or as pharmaceutically acceptable salts.
Acyl derivatives of basic aminoacids can also be used in the present invention. C.sub.2-6 acyl aminoacids which are linear or branched can be used. These acids are well known to the pharmacologists and to the skilled of pharmaceutical technique. Particularly preferred acyl groups are acetyl, propionyl, butyryl, valeryl and isovaleryl.
Suitable pharmaceutical salts can be formed between the above basic aminoacids and any conventional anion such as chloride, bromide, iodide or an acid aspartate such as aspartate, an acid citrate such as citrate, an acid tartrate such as tratrate, an acid phosphate such as phosphate, an acid fumarate, a glycophosphate such as glucophosphate, acid lactate, acid maleate, orotate; acid oxalate, particularly oxalic acid; a sulfate, particularly preferably sulfate, trichloroacetate, trifluoroacetate and methanesulfonate.
Examples of illnesses or disorders characterized by elevated levels of ceramide include inflammatory bowel diseases, diffuse intravascular coagulation, fever, protein catabolism and/or lipid depletion, hepatosplenomegaly associated with inflammatory or metabolic liver diseases, endo-myocarditis, endothelial cells and leucocytes activation, capillary thrombosis, meningo-encephalitis due to infectious agents, organ transplantation, rheumatoid arthritis and connective tissue diseases, and autoimmune diseases, hyperthyroidism, damages by radiations and/or chemotherapy agents and chronic fatigue syndrome.
Since the use of some drugs can also induce high levels of ceramide, the present invention also contemplates decreasing ceramide levels in patients treated with such a drug. For example, a basic aminoacid in accordance with the present invention can be coadministered with corticoseroids (such as dexamethasone), anti-inflammatory (such as indomethacin), antiviral (such as interferon), immunosuppressants (such as cyclosporin), chemotherapy agents (such as adriamicin), immunopotentiants (such as immunoglobulins and vaccines) and endocrinological agents (such as metimazole) to prevent increased levels of ceramide.
Normal levels of ceramides in healthy patients depend on the age, size and weight of the individual, but are in general within the range of from 5 to 50 picomoles/10.sup.6 cells (preferably, lymphocytes of peripheral blood). Levels higher than 50 picomoles/10.sup.6 cells are regarded as high levels. The use of basic aminoacids, acylated basic aminoacids and pharmacologically acceptable salts thereof of the present invention reduce such high levels by at least 25%.
In general, the basic aminoacids are administered in accordance with the present invention in concentrations which reduce ceramide levels by at least 25%. Suitably, this result is achieved by administering 50 mg to approximately 15 g/day of basic aminoacids by oral or parenteral route. Preferably, high levels of these basic aminoacids should be administered, i.e., &gt;1 g per day, &gt;2 g per day; particularly preferably, 4-10 g per day.
Monitoring ceramide levels can be conducted either by directly monitoring ceramide levels in a cell (such as a lymphocyte) or by indirectly monitoring the concentrations of a ceramide metabolite in a cell. Preferably, the patient's ceramide levels are monitored both prior to and following administration of the basic aminoacid in order to assess the amount of reduction. Monitoring can begin any time following administration but suitably is commenced following 3 hours to ensure accurate results. Monitoring can be continued indefinitely.
Ceramide levels can be directly measured by isolating peripheral blood lymphocytes from the patient. Thereafter the cells are centrifuged to eliminate the supernatant, and the lipids are removed from the cell pellet. The organic phase containing the ceramide can be assayed using the "DAG kinase assay" for phosphorylating the ceramide which is then evidenced by autoradiography [Cifone, M. G. et al., J. Exp. Med., 180(4): 1547-52].